Studies in the coming year (09-01-79 through 08-31-80) will include: 1. Signs and sequences in rapid, synchronously induced vitamin A deficiency. Ongoing studies of the interrelationships between the many and diverse signs of deficiency will be continued to gain a better understanding of cause-effect relationships. 2. Metabolite patterns. Screening of tissue, plasma, and urinary amino acid and metabolite levels as a function of time after onset of deficiency will be expanded. 3. Hypertauremia. The origin of urinary taurine in vitamin A deficient rats will be determined using 35S - or 14C-labeled precursors. 4. Impaired drug metabolism. Efforts will be made to determine which form(s) of cytochrome P450 are depressed in vitamin A deficiency. 5. Vitamin D and calcium excretion. Hydroxylated D forms will be quantitated and compared with the decrease in cytochrome P450 levels observed in vitamin A deficiency. 6. Cellular receptors. The nature of the bindng of retinol to non-cytosol protein(s) will be further investigated. 7. Immune responses. Studies of the relative effect of vitamin A deficiency on local and systemic humoral immune responses, and cell-medated immune responses will be continued.